1. Field of the Invention
Aspects of the present invention relate to a composite anode active material, a method of preparing the same, an anode containing the composite anode active material, and a lithium battery containing the composite anode active material, and more particularly, to a composite anode active material containing a solid solution, a method of preparing the same, an anode containing the composite anode active material, and a lithium battery containing the composite anode active material.
2. Description of the Related Art
Non-aqueous electrolyte secondary batteries using lithium compounds as anodes have high voltages and high energy densities. Specifically, metallic lithium has become the subject of intense research because of the resultant high battery capacity. However, metallic lithium is sensitive to heat or external impacts and is even explosive due to its instability and high reactivity. Furthermore, when metallic lithium is used as an anode material, a large amount of lithium may be deposited on the surface of the anode in the form of a dendrite, which may degrade charge and discharge efficiencies or cause internal-shorts between the anode and the cathode.
A carbonaceous anode performs redox reactions such that lithium ions existing in an electrolytic solution undergo intercalation/deintercalation in the carbonaceous anode having a crystal lattice structure during charge and discharge cycles, which is referred to as a “rocking chair type” anode. The carbonaceous anode is stable due to its porosity which allows the carbonaceous carbon to undergo less change in volume during charge and discharge cycles. For example, graphite, which is a highly crystalline material, when being made into a structure in the form of LiC6, has a theoretical specific capacity of about 372 mAh/g. This is only about 10% of the capacity of metallic lithium, i.e., 3860 mAh/g. Meanwhile, a metal such as silicon or tin, or a lithium-containing alloy, such as lithium-aluminum, lithium-lead, lithium-tin, or lithium-silicon, has a higher electrical capacity than a carbonaceous material. However, when such an alloy of two or more metals or a single metal is used as an anode, lithium dendrite may be formed or a considerable volume change in the volumetric expansion/shrinkage of the metal may occur.
Therefore, there are many efforts to solve such problems of the anode material. For example, JP 1997-249407 discloses a composite of silicon and a carbonaceous material, such as graphite.